Well to make things clear :
Yes uh19 is based on th99's database. That means initially their content was identical and that we inherited their mistakes. However as time passed we've added many features which we had to add ourself.
Sometimes we tried to use shortcuts which failed completely (form factors are just inaccurate) or added the feature but still needs some human review to be usable (ram slots and some I/o ports).
However the rest is mostly accurate (this problem with expansion slots did happen like 3 times in 9 months).
Meanwhile TH99 is also filled with errors, mistakes, etc. However there's nobody to fix them. For win3x there's a team that can fix them for you if you tell them 😀
(Or we just figure it out ourselves).
Here's an example of a pretty bad mistake from TH99 :
8 entries ... With various degrees of accuracy (some even mention a 386SX)
Did abit make this many boards ? No. They made just one : http://www.win3x.org/uh19/motherboard/show/60
Maybe there were some revisions, but th99's revision system isn't accurate either (they're based on manual revision which is different from board revision), and it doesn't justify making this mess.
And examples like this are countless.